Pour boiling water over wild rice.
Cover and let stand 15 minutes.
Drain.
Add soup, mushrooms and liquid, 1/2 cup water and seasonings.
Saute onion in oil until lightly browned.
Add ground beef and cook until lightly browned, breaking into small pieces with fork.
Mix onion and beef with rice mixture.
Spoon into buttered 2-quart casserole and bake in a 325° F.oven for 1 hour.
This casserole may be prepared in advance, refrigerated and baked at serving time.
Add 15 minutes to baking time